Addition of a boost to the tumor bed following a course of whole-breast irradiation is effective for treating positive margins?

• A meta-analysis demonstrated that a positive surgical margin:
  • Defined as the presence of invasive disease or ductal carcinoma in situ on ink:
    • Is associated with at least a 2-fold increase in the risk of ipsilateral breast tumor recurrence (IBTR):
      • Odds ratio, 1.96:
        • Which has been confirmed by other series
• While a boost may partially mitigate the effect of a positive surgical margin:
  • The risk of a local failure:
    • Remains higher than in a patient with a cleared surgical margin treated with boosted whole-breast irradiation
• Furthermore, a randomized clinical trial showed:
  • That increasing the boost dose:
    • Does not nullify the increased risk of local recurrence associated with a positive surgical margin:
      • 17.5% vs 10.8%:
        • P=>0.1
  • This is true regardless of the type and fractionation pattern of the radiotherapy
• Neither favorable tumor biology (including receptor status) nor the administration of systemic therapy:
  • Can completely offset the effect of a positive margin
• REFERENCES
  • Houssami N, Macaskill P, Marinovich ML, Morrow M. The association of surgical margins and local recurrence in women with early-stage invasive breast cancer treated with breast-conserving therapy: a meta-analysis. Ann Surg Oncol. 2014;21:717-730.
  • Mansfield CM, Komarnicky LT, Schwartz GF, et al. Ten-year results in 1070 patients with stages I and II breast cancer treated by conservative surgery and radiation therapy. Cancer. 1995;75:2328-2336.
  • Moran MS, Schnitt SJ, Giuliano AE, et al; Society of Surgical Oncology; American Society for Radiation Oncology. Society of Surgical Oncology-American Society for Radiation Oncology consensus guideline on margins for breast-conserving surgery with whole-breast irradiation in stage I and II invasive breast cancer. J Clin Oncol. 2014;32:1507-1515.
  • Poortmans PM, Collette L, Horiot JC, et al. Impact of the boost dose of 10 Gy versus 26 Gy in patients with early stage breast cancer after a microscopically incomplete lumpectomy: 10-year results of the randomized EORTC boost trial. Radiother Oncol. 2009;90:80-85.
  • Wazer DE, Schmidt-Ullrich RK, Ruthazer R, et al. Factors determining outcome for breast-conserving irradiation with margin-directed dose escalation to the tumor bed. Int J Radiat Oncol Biol Phys. 1998;40:851-858.

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